根据条件的列数

Question

我创建了一个oracle查询，如下所示，查询工作正常 ，但问题是，我想要一个更多的列，这是名称的计数，其中类别应该是A和ID应该在1

SELECT name, velocity, COUNT(*) AS count, category FROM section GROUP BY name, velocity 

谁能告诉我，这

Answer 1

SELECT name, velocity, COUNT(*) AS count, 
COUNT(CASE WHEN category = 'A' AND id = 1 THEN 1 END) 
FROM section 
GROUP BY name, velocity 

这应该工作。

如果记录不符合条件，那么它将返回一个NULL，并且count跳过NULL字段。

Answer 2

SELECT name, velocity, COUNT(*) AS count, category, 
     (select count(distinct name) from section where category = 'A' and id = 1) 
FROM section 
GROUP BY name, velocity 

Answer 3

事情是这样的一些解决方案：

SELECT name, velocity, COUNT(*) AS count, 
SUM(CASE WHEN category = 'A' AND id = 1 THEN 1 ELSE 0 END) 
FROM section 
GROUP BY name, velocity